This study assessed the relationships between the energy efficiency of productive energy (Arkansas Net Energy; PE) or classic net energy (CNE) and heat increment (HI), net energy (NE) for gain (NEg) or maintenance (NEm), performance, protein accretion, and dietary total digestible amino acids (TDAA) or digestible CP (dCP). Eight experiments were conducted, each with 240 day-old chicks distributed in 12 pens, each fed one of twelve diets with varying concentrations of TDAA (or dCP), digestible starch, digestible fat, and non-starch polysaccharides. All birds were placed at the same time. Each experiment received the test diets for seven days starting each week, one after the other. A digestibility study determined N-corrected apparent metabolizable energy (AMEn). Variables measured were BW gain (BWG), feed conversion ratio (FCR), protein accretion (PAC; g/bird per day), efficiency of PAC (PACe; g/kg), fat gain (FG, g/bird per day), and energy gain (NEg; kcal/kg) with Dual-Energy X-Ray Absorptiometry, fed (HP) and fasting (FHP) heat production (FHP = NEm; kcal/kg), HI (kcal/kg), CNE (CNE = AMEn – HI; kcal/kg), total NE (NEt; = NEg + NEm; PE is Net; kcal/kg), PE efficiency (PE/AMEn), and CNE efficiency (CNE/AMEn). A mixed models design, with 12 treatments, eight replications, and the experiment set as the random factor, was used to assess pairwise relationships in JMP. NEg and NEm explained 95% of the variability in PE/AMEn (P < 0.001); however, HI showed no influence on PE/AMEn (P = 0.814). HI explained 98% of the variability in CNE/AMEn (P < 0.001); however, NEg or NEm showed no influence on CNE/AMEn (P ≥ 0.534). Improvements in PACe or FCR increased the PE/AMEn efficiency but reduced the CNE/AMEn efficiency (P < 0.05). Higher BWG increased PE/AMEn and CNE/AMEn (P = 0.001). TDAA or dCP favored PAC and FCR (P < 0.008). Higher PACe values were associated with increased HI, NEg, and NEt, whereas PAC rose the NEm (P < 0.03).